Circuit for monitoring battery voltage with ADC?

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I would like to monitor the voltage of a LiPo battery pack that powers my AVR. Can I simply connect the 3.7v positive terminal of the battery to an ADC channel on my ATmega16? Or is it more complicated?

I've attached a simple schematic of the circuit that I've described.

Thanks in advance.

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I'd say you need to use a 3.3V regulator, and monitor the 3.7V thru a voltage divider, like a couple of 10K resistors.

Imagecraft compiler user

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Yeah you're right I should be using a boost regulator. I've always used a 9V battery and a LM7805 in the past that I was mistaken when I made this drawing.

Is the basic concept of connecting the power terminal of the battery to the ADC sound?

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Ya, that will work...

You could connect Aref to 5v or if you want full scale, use a resistive divider from the 5v volt line to set Aref to 3.7v...

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Quote:
You could connect Aref to 5v or if you want full scale

If Aref = 5V, 4.9V, 4.8V, 4.7V, 4.6V, 4.5V, 4.4V,...
and the V+ is fed into the ADC input then one will always read that the V+ = Full Scale.

If the Vref is set to a reference that is truely independant of V+, i.e. a true reference voltage, then one can compare the slowly decreasing V+ against that FIXED reference. In practice, one might monitor V+/2, (through a resistive divider), and use a fixed reference, either internal, or external, (depending on the uC used...).

JC

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Thanks for the replies. I feel confident to move forward with my design.

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If Vcc down to 2.7 volts is acceptable you could run the L version directly off the battery. Then get the battery voltage by measuring the internal 1.22v bandgap voltage using Vcc as a reference. That saves an io pin too.